Hello,
So If I understand you correctly you explicitly invoke System.gc() and
get long pauses for that call. Simple Solution: remove the call to
System.gc() and tune from there. Worse (possible) solution: try setting
-XX:+/ExplicitGCInvokesConcurrent/
Setting /ExplicitGCInvokesConcurrent /may or may not have some
unintended side effects. I strongly recommend to remove all calls to
System.gc that are not for debugging/maintenance.
Best Regards,
Thorsten
//
Am 28/06/2021 um 19:39 schrieb Stefan Reich:
Hi Thorsten!
Does MaxGCPauseMillis apply to System.gc() too? I thought this was for
the incremental collections.
> Did you parse gc logs or by hand/feel?
What, do you think I'm a beginner??? :D
Joke aside, yes it was just "by feel". I know I should measure it
properly. Is timing the call to System.gc() an acceptable way to
measure this? As far as I know, it only returns after GC has actually
completed.
> If you are certain that you don't need more than 800mb of live
objects, limit the maxheap to something like 1.5 gb.
Hmm, I am rather not that certain about that... I'd like to keep the
max heap around 6 GB.
On Mon, 28 Jun 2021 at 09:35, Thorsten <t...@freigmbh.de
<mailto:t...@freigmbh.de>> wrote:
Hello,
You should not get seconds long stop the world event. How did you
measure the pauses? Did you parse gc logs or by hand/feel?
The desired max pause for g1 can be tuned using
|-XX:MaxGCPauseMillis=200|
|, so 200 ms max pause should be the default.
|
It would be helpfull if you take gc logs and provide them. What
java version are you using? In old java versions g1 is fairly bad,
quality improves in newer versions.
You can tune and change the garbage collector using -XX Options,
see for example here
https://ionutbalosin.com/2020/01/hotspot-jvm-performance-tuning-guidelines/
<https://ionutbalosin.com/2020/01/hotspot-jvm-performance-tuning-guidelines/>
Maybe you find one of the experimental garbage collectors helpfull
for your application.
Another simple "Hack" to tune your gc speed: If you are certain
that you don't need more than 800mb of live objects, limit the
maxheap to something like 1.5 gb. That way your app is simply
unable to collect gigabytes of garbage and your max pauses will go
down.
Best regards,
Thorsten
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--
Stefan Reich
BotCompany.de // Java-based operating systems
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